The overall objective of this proposal is to investigate how the available retinal and extraretinal oculomotor signals are used in the control of eye movements and eye-hand coordination, and in the encoding of visual space, in normal and pathological settings. Specifically, the aim is to understand the role played by ocular proprioception in the immediate on- line and adaptive control of eye movements and visually-guided limb movements. Three specific hypotheses will be addressed, concerning potential immediate and long-term functions of ocular proprioception: 1) proprioception contributes to the immediate on-line encoding of orbital eye position 2) proprioception participates in the adaptive processes that ensure an accurate internal representation of orbital eye position; 3) proprioception does not contribute to the on-line signal used in the feedback control of saccadic pulse generation. These hypotheses will be investigated in rhesus monkeys by measuring and comparing egocentric and oculocentric spatial localization (as manifest in visually-guided pointing) and oculomotor function (static ocular alignment and saccade metrics), in paradigms where. visual inputs are altered, and where proprioceptive afference is modified or eliminated. Specifically, the effect of unilateral and bilateral ocular deafferentation on eye and limb movements, will be investigated in normal monkeys, during passive eye deviation, prism adaptation, parametric saccadic adaptation, and adaptation to unilateral ocular muscle palsies. Eye movements will be measured with the magnetic search coil method; pointing will be quantified with a computer touch- screen. The proposed research will help to elucidate the role played by ocular proprioception in eye and limb motor control, and in visuo-spatial perception. Potential health care implications include advances in the understanding and therapy of a variety of visual, oculomotor, and skeletal-motor disorders, such as strabismus and the limb- gait ataxia associated with ocular muscle palsies. The research proposal integrates training in experimental and theoretical approaches to motor control, clinical experience with related disorders, and medical student and resident teaching.